1. Technical Field
The present invention relates to a webbing take-up device including a tension reducer which can make a biasing force biasing a webbing belt in a take-up direction to be small in a state in which the webbing belt which constrains an occupant's body is worn.
2. Related Art
In a webbing take-up device disclosed in Japanese Patent No. 3,396,027, a winding shaft connected to one end of a seat belt take-up shaft is rotatably supported by a housing. The end of a main power spring, which generates a biasing force in a direction (take-up direction) in which a seat belt is taken up around the seat belt take-up shaft as the seat belt is pulled out from the seat belt take-up shaft, is locked to this winding shaft, and a ratchet wheel which constitutes a so-called tension reducer is rotatably supported.
In the tension reducer applied to this webbing take-up device, the inner end of a subsidiary power spring in the spiral direction of which the outer end in the spiral direction is locked to a ratchet wheel engages frictionally with the winding shaft via a ring or a spring clutch.
When the main power spring rotates the winding shaft in the take-up direction in a state in which a ratchet claw of a rotation regulating mechanism has regulated the rotation of the ratchet wheel in the take-up direction, the inner end of the subsidiary power spring in the spiral direction rotates in the take-up direction with respect to the outer end in the spiral direction in a state in which the rotation in the take-up direction has been regulated via the ratchet wheel. Thereby, the biasing force of the main power spring is offset by the biasing force generated in the subsidiary power spring.
In the tension reducer applied to this webbing take-up device, the inner end of the main power spring in the spiral direction is locked to the winding shaft which has passed through the ratchet wheel. However, when the inner end of the main power spring in the spiral direction within a case member is locked to the winding shaft which has passed through the ratchet wheel, the inner end of the main power spring in the spiral direction is hidden by the ratchet wheel or the case member, and thus, it is difficult to operate.